The age of light-duty vehicles in the United States rose 13 percent to an average of 10.5 years, according to a 2017 survey by the U.S. Department of Transportation. While this number is off the average of 11.6 years cited by research firm IHS in 2016, all signs point to America's fleet—and its population of more than 223 million licensed drivers—growing older.

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Pickup trucks, in particular, are staying on for longer. The Energy Information Administration, reporting on the DOT survey, said the average pickup was 13.6 years old in 2017 as compared to 11.2 in 2009. Vans jumped to 10.9 years (up 24 percent), SUVs rose to 8.5 years (up 20 percent), and cars' average age increased to 10.3 years (up 8 percent).

"Overall, the aging of the vehicle fleet suggests many households have delayed purchasing a new vehicle or have instead purchased a used vehicle," the EIA noted.

Lower-income households were most likely to hold on to older cars. On average, those reporting annual incomes of less than $25,000 drove 13-year-old cars, while those with incomes above $100,000 had nine-year-old cars. An influence apart from income, however, is the increasing glut of used cars, driven by record levels of leasing and low finance rates during the past several years. The website Edmunds.com reported an all-time high of 39.2 million used-vehicle sales in 2017 and average used-vehicle prices that climbed 1.4 percent in 2017, compared with an average hike of 3.6 percent between 2012 and 2016.

Paying significantly less for one-time sales taxes and less still on annual payments for vehicle property taxes and insurance premiums are even greater incentives for anyone to keep an older car running. Go ahead: now's the perfect time for that 1978 Chrysler LeBaron Medallion.